In the prior art, there are numerous wire feed mechanisms but they operate at uniaxial compression stresses that are too low for the intended wire processing needs and push the wire with driven pinch rollers that contact the wire only over the very short span when the rollers meet. The available methods for producing high uniaxial compression stresses in the wire all apply multi-axial compression generally in the form of hydrostatic pressure, are high cost, have a single diameter feed stock and are usually used to extrude soft metals through large reductions.
Prior art wire feeding devices that are used to move wire with pinch rolls advance the wire with relatively low driving force capability. These devices are used in conjunction with devices that operate on the wire without requiring the use of high forces generated by the wire feed apparatus. Examples of low force wire feeding devices for general use are shown in U.S. Pat. Nos. 5,427,295, 6,557,742. U.S. Pat. No. 7,441,682 shows a device for feeding welding wire and the apparatus of U.S. Pat. No. 6,044,682 feeds wire to a set of wire shaping devices.
The manufacturing of coil springs by the deflection coiling using a pair of opposing drive rolls to grip and axially move the wire through a guide tube and against forming points to create a coil spring is shown in U.S. Pat. No. 7,082,797. All prior art devices use rigid, close clearance guide tubes to prevent the moving wire from unstable bending as it moves from the rolls to its destination. The wire is forced against tooling components that cause it to bend in the desired manner and in so doing create a resistance to the wire's motion that results in an axial compression stress in the wire. This prior art method is not capable of creating a sufficiently high axial compression stress states in the wire. First, the gripping action on the wire is provided by one or at most two pinch roller gripping stations.
For the most part, prior art that is in the field of continuous extrusion of wire fall into the categories of:
(a) mechanical extrusion in which the rod to be extruded moves along with a confining container as it is pushed into and through the stationary reduction die; or
(b) hydrostatic extrusion in which the rod to be extruded is surrounded by high pressure fluid as it enters the reduction die.
Briefly, the continuous extrusion type processes are industrially known as:
1. Conform type continuous extrusion uses a circumferential groove in a rotating wheel to transport the rod into a zone in which the groove is covered by a stationary shoe that has an abutment that protrudes into the groove and blocks the rod from continuing to move along with the wheel groove and thus creates a pressure at the abutment which forces the rod to extrude through an orifice in the stationary shoe adjacent to the abutment. U.S. Pat. Nos. 3,765,216, 3,872,703, 4,227,968, 5,097,693, 5,335,527 and 4,094,175 are illustrative of this type of extrusion. The rod never leaves contact with the wheel groove before it enters the rod extrusion operation.
2. Linex type continuous extrusion might be considered a linear version of Conform type apparatus in that the gripping force on the feed stock is derived from the friction force applied by opposing gripping and moving, tractor tread like surfaces while the feedstock is being constrained on the other two sides as it is driven into an extrusion die. The feed stock is rectangular in cross section with the moving surfaces grip the wide face of feedstock and narrow faces lubricated. U.S. Pat. Nos. 3,922,898 and 4,262,513 are illustrative of this type of extrusion.
Friction drive continuous extrusion apparatus, that captures the feedstock bar in opposing roll grooves much like a rolling mill and drives the feedstock bar into a reduction die that is placed into the cavity formed by the mating roll groves and that blocks the exit of the rod or wire from leaving the moving grooves without passing through the die are illustrated in U.S. Pat. Nos. 3,934,446 and 4,220,029. Again the rod never leaves contact with the wheel groove before it enters the extrusion operation.
None of the above apparatus are suitable for extruding a wire form feedstock that is the continuous wire-to-wire extrusion application in which the wire must leave contact with the drive wheel before encountering the extrusion die.
The prior art on continuous hydrostatic extrusion of a wire product from a rod feed stock using some form of viscous fluid drag to develop a fluid pressure profile along the rod is in three forms:                a) Viscous drag consisting of a viscous fluid being circulated through a series of cavities that surround a central passage through which the rod to be extruded passes and such that the moving fluid acts on the rod in viscous shear manner to build up an axial compressive stress in the rod and force the rod through the die by hydrostatic extrusion as shown in U.S. Pat. No. 3,731,509.        b) Segmented Moving Chamber type using a pressure chamber that is constructed of multiple, wedge shaped extrusion chamber sections that move in a “tractor tread” manner with four “tractor tread” assemblies that bring the moving chamber segments together to form a continuously moving pressure chamber with a bore that transmits surface shear forces to the feedstock through a viscous medium and pushes it through a die in a form of hydrostatic extrusion as shown in U.S. Pat. No. 4,633,699.        c) Rotating grooved wheel and groove covering stationary shoe comprise the dominant components of this apparatus in which viscous fluid is injected under pressure along the enclosed passage to co-act with the rotating wheel groove and build the pressure in the viscous fluid as it approaches the extrusion die. The use of the moving wheel shearing of the viscous fluid builds the fluid pressure to cause hydrostatic extrusion as shown in U.S. Pat. No. 4,163,377.        
None of the above apparatus are suitable for extruding a wire feedstock in a continuous wire-to-wire extrusion application.
Continuous, hydrostatic extrusion process for wire-to-wire reduction is given as shown in U.S. Pat. No. 3,841,129. In this apparatus, the wire is drawn into a high pressure chamber through a seal [which is represented as a wire drawing operation] by a capstan rotating within the large high pressure chamber. Then the wire leaves the capstan and goes to an extrusion die where it leaves the high pressure chamber by the process of hydrostatic extrusion. Also, patentee's proposed apparatus has numerous friction related energy losses between the moving parts and the moving parts in the high pressure viscous pressurizing medium that would substantially reduce the efficiency and durability of the apparatus.